[Biology Class Notes] on Electrocardiograph Pdf

ECG stands for electrocardiograph. It gives a graphical representation of the electrical activity of the heart during a cardiac cycle which helps to further detect the abnormalities and help us to measure the functioning of the heart. To obtain a standard ECG graph, a patient is connected to the machine with three electrical leads, one to each wrist and to the left ankle, that continuously monitor the heart activity and functioning. The human heart produces an electrical impulse passing through our heart, it generates an electrical impulse by itself. 

Explanation of ECG Different Waves

There are mainly three different types of ECG is performed:

• Resting ECG: When your body is in resting state. Under this type machine examine your heart beat during resting condition. 

• Ambulatory ECG: This type of ECG is conducted for 24 hours. The heart’s electrical impulses are measured by a device called the Holter Monitor.

• Cardiac Stress Test: This test is used to measure ECG when you are on an exercise bike.

Different Types of Waves Produced by Electrocardiogram

1. The P-Wave

It  represents the electrical excitation (or depolarisation) of the atria, which leads to the contraction of both the atria. Features of P – Wave P duration < 0.12 secP amplitude < 2.5 mm Frontal plane P wave axis: 00 to +750 May see notched P waves in frontal plane

2. The QRS Complex

It represents the repolarization of the ventricles, which initiates the ventricular contraction. Features of QRS Complex QRS duration ≤ 0.10 secQRS amplitude varies from lead to lead and also from person to person. Two determinants of QRS voltages are:Size of the ventricular chambers (i.e., the larger the chamber, the larger the voltage)Nearness of chest electrodes to ventricular chamber (the closer, the larger the voltage)

3. T-Wave

It represents the return of the ventricles from excited to normal state (repolarisation) and the end of the T-wave marks the end of systole. The normal peak of the T wave is usually in the same direction as the QRS wave except in the right precordial leads. In the normal ECG the T wave is always upright. By counting the number of QRS complexes that occur in a given time period, a person can determine the heart beat rate of an individual. 

ECG Graph

Electrocardiograph Machine Includes

They have small sticky electrodes attached to the arms, chest, legs. These electrodes are connected to the ECG machine with the help of  wires that help in detecting the electrical impulses occurring at each heartbeat. These electrodes can detect every minute form of changes happening in  heart muscles and draw every depolarising pattern of heartbeat on a graph.

Feature of Normal ECG Heart beat should be in between 60-90 beats per minute (bpm).

• PR Interval: 0.12 – 0.20 sec

• QRS Duration: 0.06 – 0.10 sec

• QT Interval (QTc ≤ 0.40 sec)

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Why is  an ECG Done? 

• ECG is done to determine or detect Abnormal heart rhythm (arrhythmias) 

• If there are any  blocked or narrowed arteries in your heart (coronary artery disease) are causing chest pain or a heart attack. 

• To find whether  you have had a previous heart attack or not.

• To monitor if the medicines are causing any side-effects to our body system.

Medical Use of ECG

The main function of ECG is to obtain information regarding the heart impulse. There is a great medical use of this information regarding your health issues like:

Chest pain Shortness of breath Light

headedness Dizziness Fainting spells It is also required prior to any type of heart surgery, including surgery for pacemaker placement.

MCQ Questions on ECG

1. ECG (Electrocardiogram) Was Developed First By

(a) Wilhelm His

(b) Steward

(c) Hubert Mann

(d) Willem Einthoven

Answer: (d)

2. This Is the Classic ECG Change in MI (Myocardial Infarction)

(a) ST-segment elevation

(b) T-wave inversion

(c) Development of an abnormal Q wave

(d) All of these

Answer: (d)

3. In Which of These Conditions Can Widened QRS and Tall-Tented T Waves Be Observed

(a) Hyponatremia

(b) Hyperkalemia

(c) Hyperglycemia

(d) Hyperphosphatemia

Answer: (b)

4. A Particular ECG Change Observed in Hypokalemia is

(a) ST Segment elevation

(b) U Wave(a position deflection after the T wave)

(c) Tall peaked T waves

(d) Widening of the QRS complex and increased amplitude

Answer: (b)

5. ECG Report Must Consist of the Following Information

(a) Rhythm, cardiac axis

(b) Conduction intervals

(c) Description of the ST segments, QRS complexes, T-waves

(d) All of these

Answer: (d)

6. For the Normal Heartbeat, Depolarization Stimulus Originates In

(a) His-bundle areas

(b) Epicardium

(c) Sinoatrial (SA)node

(d) Atrioventricular (AV) node

Answer: (c)

7. The Characteristics – Slurring of the Initial QRS Deflection, Shortened PR Interval, and Prolonged QRS Duration Are of This Condition

(a) Atrial tachycardia

(b) Left bundle branch block

(c) WPW (Wolff-Parkinson-White) syndrome

(d) Myocardial ischemia

Answer: (c)

8. P Wave Indicates

(a) Depolarization of right ventricle

(b) Depolarization of left ventricle

(c) Depolarization of both atria

(d) Atrial to ventricular conduction time

Answer: (c)

9. Ventricular Muscle Depolarization Is Indicated By

(a) PR interval

(b) P wave

(c) U wave

(d) The QRS complex

Answer: (d)

10. ECG Identified by the PR Interval Tends to Become Longer With Every Succeeding ECG Complex Until There Is a P Wave Not Followed by a QRS is Observed in

(a) Third-Degree Atrioventricular Block

(B) Second-Degree Atrioventricular Block, Type II

(C) Second-Degree Atrioventricular Block, Type I

(D) First-Degree Atrioventricular Block, Type II

Answer: (c)

What is Electrocardiogram?

The process by which an electrocardiogram is produced is known as electrocardiography. The process involves a graphical representation of the Heart impulses. In simple words, a graph of voltage versus time of the electrical activity of the heart using electrodes which are placed on the skin is known as an electrocardiogram. The electrodes used in this particular process are used to detect the small electrical charge that are the consequences of the cardiac muscle depolarization followed by repolarization.

Medical Uses Related to Heart Cardiography

This particular process helps in a lot of medical uses which are related to heart issues. Some of the common medical issues which are solved using this particular process can be listed as described below:

• This process is carried out in times when a person gets chest pain or myocardial infarction which is also known as heart attack. This this includes ST elevated myocardial infarction (STEMI) or non ST elevated myocardial infarction (NSTEMI)

• If a person has shortness of breath or murmurs, fainting seizures, funny turns or have arrhythmias, then the process is very useful in order to know the internal issues which are causing the particular symptoms.

• It is highly useful in cardiac stress testing.

• It is highly used in electrolyte abnormalities such as hyperkalemia.

• CTA (computed tomography angiography) MRA (magnetic resonance angiography) of the heart are done by the following process which we know widely as electrocardiography.

The world in recent times has recorded a large number of people losing their life due to heart infarction. This process is carried out sometimes in a continuous monitoring process for the most ill patients, those who need special care and medical attention.